diff options
Diffstat (limited to 'man/systemd-run.xml')
| -rw-r--r-- | man/systemd-run.xml | 684 |
1 files changed, 684 insertions, 0 deletions
diff --git a/man/systemd-run.xml b/man/systemd-run.xml new file mode 100644 index 0000000..5be9823 --- /dev/null +++ b/man/systemd-run.xml @@ -0,0 +1,684 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="systemd-run" + xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>systemd-run</title> + <productname>systemd</productname> + </refentryinfo> + + <refmeta> + <refentrytitle>systemd-run</refentrytitle> + <manvolnum>1</manvolnum> + </refmeta> + + <refnamediv> + <refname>systemd-run</refname> + <refpurpose>Run programs in transient scope units, service units, or path-, socket-, or timer-triggered service units</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <cmdsynopsis> + <command>systemd-run</command> + <arg choice="opt" rep="repeat">OPTIONS</arg> + <arg choice="plain"><replaceable>COMMAND</replaceable> + <arg choice="opt" rep="repeat">ARGS</arg> + </arg> + </cmdsynopsis> + <cmdsynopsis> + <command>systemd-run</command> + <arg choice="opt" rep="repeat">OPTIONS</arg> + <arg choice="opt" rep="repeat">PATH OPTIONS</arg> + <arg choice="req"><replaceable>COMMAND</replaceable></arg> + <arg choice="opt" rep="repeat">ARGS</arg> + </cmdsynopsis> + <cmdsynopsis> + <command>systemd-run</command> + <arg choice="opt" rep="repeat">OPTIONS</arg> + <arg choice="opt" rep="repeat">SOCKET OPTIONS</arg> + <arg choice="req"><replaceable>COMMAND</replaceable></arg> + <arg choice="opt" rep="repeat">ARGS</arg> + </cmdsynopsis> + <cmdsynopsis> + <command>systemd-run</command> + <arg choice="opt" rep="repeat">OPTIONS</arg> + <arg choice="opt" rep="repeat">TIMER OPTIONS</arg> + <arg choice="req"><replaceable>COMMAND</replaceable></arg> + <arg choice="opt" rep="repeat">ARGS</arg> + </cmdsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><command>systemd-run</command> may be used to create and start a transient <filename>.service</filename> or + <filename>.scope</filename> unit and run the specified <replaceable>COMMAND</replaceable> in it. It may also be + used to create and start a transient <filename>.path</filename>, <filename>.socket</filename>, or + <filename>.timer</filename> unit, that activates a <filename>.service</filename> unit when elapsing.</para> + + <para>If a command is run as transient service unit, it will be started and managed by the service manager like any + other service, and thus shows up in the output of <command>systemctl list-units</command> like any other unit. It + will run in a clean and detached execution environment, with the service manager as its parent process. In this + mode, <command>systemd-run</command> will start the service asynchronously in the background and return after the + command has begun execution (unless <option>--no-block</option> or <option>--wait</option> are specified, see + below).</para> + + <para>If a command is run as transient scope unit, it will be executed by <command>systemd-run</command> + itself as parent process and will thus inherit the execution environment of the caller. However, the + processes of the command are managed by the service manager similarly to normal services, and will show + up in the output of <command>systemctl list-units</command>. Execution in this case is synchronous, and + will return only when the command finishes. This mode is enabled via the <option>--scope</option> switch + (see below).</para> + + <para>If a command is run with path, socket, or timer options such as <option>--on-calendar=</option> (see below), + a transient path, socket, or timer unit is created alongside the service unit for the specified command. Only the + transient path, socket, or timer unit is started immediately, the transient service unit will be triggered by the + path, socket, or timer unit. If the <option>--unit=</option> option is specified, the + <replaceable>COMMAND</replaceable> may be omitted. In this case, <command>systemd-run</command> creates only a + <filename>.path</filename>, <filename>.socket</filename>, or <filename>.timer</filename> unit that triggers the + specified unit.</para> + + <para>By default, services created with <command>systemd-run</command> default to the + <option>simple</option> type, see the description of <varname>Type=</varname> in + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> for + details. Note that when this type is used, the service manager (and thus the + <command>systemd-run</command> command) considers service start-up successful as soon as the + <function>fork()</function> for the main service process succeeded, i.e. before the + <function>execve()</function> is invoked, and thus even if the specified command cannot be started. + Consider using the <option>exec</option> service type (i.e. <option>--property=Type=exec</option>) to + ensure that <command>systemd-run</command> returns successfully only if the specified command line has + been successfully started.</para> + + <para>After <command>systemd-run</command> passes the command to the service manager, the manager + performs variable expansion. This means that dollar characters (<literal>$</literal>) which should not be + expanded need to be escaped as <literal>$$</literal>. Expansion can also be disabled using + <varname>--expand-environment=no</varname>.</para> + </refsect1> + + <refsect1> + <title>Options</title> + + <para>The following options are understood:</para> + + <variablelist> + <varlistentry> + <term><option>--no-ask-password</option></term> + + <listitem><para>Do not query the user for authentication for + privileged operations.</para> + + <xi:include href="version-info.xml" xpointer="v226"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--scope</option></term> + + <listitem> + <para>Create a transient <filename>.scope</filename> unit instead of the default transient + <filename>.service</filename> unit (see above). + </para> + + <xi:include href="version-info.xml" xpointer="v206"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--unit=</option></term> + <term><option>-u</option></term> + + <listitem><para>Use this unit name instead of an automatically + generated one.</para> + + <xi:include href="version-info.xml" xpointer="v206"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--property=</option></term> + <term><option>-p</option></term> + + <listitem><para>Sets a property on the scope or service unit that is created. This option takes an assignment + in the same format as + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s + <command>set-property</command> command.</para> + + <xi:include href="version-info.xml" xpointer="v211"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--description=</option></term> + + <listitem><para>Provide a description for the service, scope, path, socket, or timer unit. If not specified, + the command itself will be used as a description. See <varname>Description=</varname> in + <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + </para> + + <xi:include href="version-info.xml" xpointer="v206"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--slice=</option></term> + + <listitem><para>Make the new <filename>.service</filename> or <filename>.scope</filename> unit part + of the specified slice, instead of <filename>system.slice</filename> (when running in + <option>--system</option> mode) or the root slice (when running in <option>--user</option> + mode).</para> + + <xi:include href="version-info.xml" xpointer="v206"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--slice-inherit</option></term> + + <listitem><para>Make the new <filename>.service</filename> or <filename>.scope</filename> unit part + of the inherited slice. This option can be combined with <option>--slice=</option>.</para> + + <para>An inherited slice is located within <command>systemd-run</command> slice. Example: if + <command>systemd-run</command> slice is <filename>foo.slice</filename>, and the + <option>--slice=</option> argument is <filename>bar</filename>, the unit will be placed under the + <filename>foo-bar.slice</filename>.</para> + + <xi:include href="version-info.xml" xpointer="v246"/> + + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--expand-environment=<replaceable>BOOL</replaceable></option></term> + + <listitem><para>Expand environment variables in command arguments. If enabled, environment variables + specified as <literal>${<replaceable>VARIABLE</replaceable>}</literal> will be expanded in the same + way as in commands specified via <varname>ExecStart=</varname> in units. With + <varname>--scope</varname>, this expansion is performed by <command>systemd-run</command> itself, and + in other cases by the service manager that spawns the command. Note that this is similar to, but not + the same as variable expansion in + <citerefentry project='man-pages'><refentrytitle>bash</refentrytitle><manvolnum>1</manvolnum></citerefentry> + and other shells.</para> + + <para>The default is to enable this option in all cases, except for <varname>--scope</varname> where + it is disabled by default, for backward compatibility reasons. Note that this will be changed in a + future release, where it will be switched to enabled by default as well.</para> + + <para>See + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for a description of variable expansion. Disabling variable expansion is useful if the specified + command includes or may include a <literal>$</literal> sign.</para> + + <xi:include href="version-info.xml" xpointer="v254"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>-r</option></term> + <term><option>--remain-after-exit</option></term> + + <listitem><para>After the service process has terminated, keep the service around until it is explicitly + stopped. This is useful to collect runtime information about the service after it finished running. Also see + <varname>RemainAfterExit=</varname> in + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + </para> + + <xi:include href="version-info.xml" xpointer="v207"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--send-sighup</option></term> + + <listitem><para>When terminating the scope or service unit, send a SIGHUP immediately after SIGTERM. This is + useful to indicate to shells and shell-like processes that the connection has been severed. Also see + <varname>SendSIGHUP=</varname> in + <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + </para> + + <xi:include href="version-info.xml" xpointer="v207"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--service-type=</option></term> + + <listitem><para>Sets the service type. Also see + <varname>Type=</varname> in + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>. This + option has no effect in conjunction with + <option>--scope</option>. Defaults to + <constant>simple</constant>.</para> + + <xi:include href="version-info.xml" xpointer="v211"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--uid=</option></term> + <term><option>--gid=</option></term> + + <listitem><para>Runs the service process under the specified UNIX user and group. Also see + <varname>User=</varname> and <varname>Group=</varname> in + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> + + <xi:include href="version-info.xml" xpointer="v211"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--nice=</option></term> + + <listitem><para>Runs the service process with the specified + nice level. Also see <varname>Nice=</varname> in + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> + + <xi:include href="version-info.xml" xpointer="v211"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--working-directory=</option></term> + + <listitem><para>Runs the service process with the specified working directory. Also see + <varname>WorkingDirectory=</varname> in + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> + + <xi:include href="version-info.xml" xpointer="v240"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--same-dir</option></term> + <term><option>-d</option></term> + + <listitem><para>Similar to <option>--working-directory=</option>, but uses the current working + directory of the caller for the service to execute.</para> + + <xi:include href="version-info.xml" xpointer="v240"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>-E <replaceable>NAME</replaceable>[=<replaceable>VALUE</replaceable>]</option></term> + <term><option>--setenv=<replaceable>NAME</replaceable>[=<replaceable>VALUE</replaceable>]</option></term> + + <listitem><para>Runs the service process with the specified environment variable set. This parameter + may be used more than once to set multiple variables. When <literal>=</literal> and + <replaceable>VALUE</replaceable> are omitted, the value of the variable with the same name in the + program environment will be used.</para> + + <para>Also see <varname>Environment=</varname> in + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> + + <xi:include href="version-info.xml" xpointer="v211"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--pty</option></term> + <term><option>-t</option></term> + + <listitem><para>When invoking the command, the transient service connects its standard input, output and error + to the terminal <command>systemd-run</command> is invoked on, via a pseudo TTY device. This allows running + programs that expect interactive user input/output as services, such as interactive command shells.</para> + + <para>Note that + <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s + <command>shell</command> command is usually a better alternative for requesting a new, interactive login + session on the local host or a local container.</para> + + <para>See below for details on how this switch combines with <option>--pipe</option>.</para> + + <xi:include href="version-info.xml" xpointer="v219"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--pipe</option></term> + <term><option>-P</option></term> + + <listitem><para>If specified, standard input, output, and error of the transient service are inherited from the + <command>systemd-run</command> command itself. This allows <command>systemd-run</command> + to be used within shell pipelines. + Note that this mode is not suitable for interactive command shells and similar, as the + service process will not become a TTY controller when invoked on a terminal. Use <option>--pty</option> instead + in that case.</para> + + <para>When both <option>--pipe</option> and <option>--pty</option> are used in combination the more appropriate + option is automatically determined and used. Specifically, when invoked with standard input, output and error + connected to a TTY <option>--pty</option> is used, and otherwise <option>--pipe</option>.</para> + + <para>When this option is used the original file descriptors <command>systemd-run</command> receives are passed + to the service processes as-is. If the service runs with different privileges than + <command>systemd-run</command>, this means the service might not be able to re-open the passed file + descriptors, due to normal file descriptor access restrictions. If the invoked process is a shell script that + uses the <command>echo "hello" >/dev/stderr</command> construct for writing messages to stderr, this might + cause problems, as this only works if stderr can be re-opened. To mitigate this use the construct <command>echo + "hello" >&2</command> instead, which is mostly equivalent and avoids this pitfall.</para> + + <xi:include href="version-info.xml" xpointer="v235"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--shell</option></term> + <term><option>-S</option></term> + + <listitem><para>A shortcut for <literal>--pty --same-dir --wait --collect --service-type=exec $SHELL</literal>, + i.e. requests an interactive shell in the current working directory, running in service context, accessible + with a single switch.</para> + + <xi:include href="version-info.xml" xpointer="v240"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--quiet</option></term> + <term><option>-q</option></term> + + <listitem><para>Suppresses additional informational output + while running. This is particularly useful in combination with + <option>--pty</option> when it will suppress the initial + message explaining how to terminate the TTY connection.</para> + + <xi:include href="version-info.xml" xpointer="v219"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--on-active=</option></term> + <term><option>--on-boot=</option></term> + <term><option>--on-startup=</option></term> + <term><option>--on-unit-active=</option></term> + <term><option>--on-unit-inactive=</option></term> + + <listitem><para>Defines a monotonic timer relative to different starting points for starting the specified + command. See <varname>OnActiveSec=</varname>, <varname>OnBootSec=</varname>, <varname>OnStartupSec=</varname>, + <varname>OnUnitActiveSec=</varname> and <varname>OnUnitInactiveSec=</varname> in + <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry> for + details. These options are shortcuts for <command>--timer-property=</command> with the relevant properties. + These options may not be combined with <option>--scope</option> or <option>--pty</option>.</para> + + <xi:include href="version-info.xml" xpointer="v218"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--on-calendar=</option></term> + + <listitem><para>Defines a calendar timer for starting the specified command. See <varname>OnCalendar=</varname> + in <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>. This + option is a shortcut for <command>--timer-property=OnCalendar=</command>. This option may not be combined with + <option>--scope</option> or <option>--pty</option>.</para> + + <xi:include href="version-info.xml" xpointer="v218"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--on-clock-change</option></term> + <term><option>--on-timezone-change</option></term> + + <listitem><para>Defines a trigger based on system clock jumps or timezone changes for starting the + specified command. See <varname>OnClockChange=</varname> and <varname>OnTimezoneChange=</varname> in + <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>. These + options are shortcuts for <command>--timer-property=OnClockChange=yes</command> and + <command>--timer-property=OnTimezoneChange=yes</command>. These options may not be combined with + <option>--scope</option> or <option>--pty</option>.</para> + + <xi:include href="version-info.xml" xpointer="v242"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>--path-property=</option></term> + <term><option>--socket-property=</option></term> + <term><option>--timer-property=</option></term> + + <listitem><para>Sets a property on the path, socket, or timer unit that is created. This option is + similar to <option>--property=</option>, but applies to the transient path, socket, or timer unit + rather than the transient service unit created. This option takes an assignment in the same format as + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s + <command>set-property</command> command. These options may not be combined with + <option>--scope</option> or <option>--pty</option>.</para> + + <xi:include href="version-info.xml" xpointer="v218"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--no-block</option></term> + + <listitem> + <para>Do not synchronously wait for the unit start operation to finish. If this option is not specified, the + start request for the transient unit will be verified, enqueued and <command>systemd-run</command> will wait + until the unit's start-up is completed. By passing this argument, it is only verified and enqueued. This + option may not be combined with <option>--wait</option>.</para> + + <xi:include href="version-info.xml" xpointer="v220"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>--wait</option></term> + + <listitem><para>Synchronously wait for the transient service to terminate. If this option is specified, the + start request for the transient unit is verified, enqueued, and waited for. Subsequently the invoked unit is + monitored, and it is waited until it is deactivated again (most likely because the specified command + completed). On exit, terse information about the unit's runtime is shown, including total runtime (as well as + CPU usage, if <option>--property=CPUAccounting=1</option> was set) and the exit code and status of the main + process. This output may be suppressed with <option>--quiet</option>. This option may not be combined with + <option>--no-block</option>, <option>--scope</option> or the various path, socket, or timer options.</para> + + <xi:include href="version-info.xml" xpointer="v232"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>-G</option></term> + <term><option>--collect</option></term> + + <listitem><para>Unload the transient unit after it completed, even if it failed. Normally, without this option, + all units that ran and failed are kept in memory until the user explicitly resets their failure state with + <command>systemctl reset-failed</command> or an equivalent command. On the other hand, units that ran + successfully are unloaded immediately. If this option is turned on the "garbage collection" of units is more + aggressive, and unloads units regardless if they exited successfully or failed. This option is a shortcut for + <command>--property=CollectMode=inactive-or-failed</command>, see the explanation for + <varname>CollectMode=</varname> in + <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for further + information.</para> + + <xi:include href="version-info.xml" xpointer="v236"/></listitem> + </varlistentry> + + <xi:include href="user-system-options.xml" xpointer="user" /> + <xi:include href="user-system-options.xml" xpointer="system" /> + <xi:include href="user-system-options.xml" xpointer="host" /> + <xi:include href="user-system-options.xml" xpointer="machine" /> + + <xi:include href="standard-options.xml" xpointer="help" /> + <xi:include href="standard-options.xml" xpointer="version" /> + </variablelist> + + <para>All command line arguments after the first non-option argument become part of the command line of + the launched process.</para> + </refsect1> + + <refsect1> + <title>Exit status</title> + + <para>On success, 0 is returned. If <command>systemd-run</command> failed to start the service, a + non-zero return value will be returned. If <command>systemd-run</command> waits for the service to + terminate, the return value will be propagated from the service. 0 will be returned on success, including + all the cases where systemd considers a service to have exited cleanly, see the discussion of + <varname>SuccessExitStatus=</varname> in + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + </para> + </refsect1> + + <refsect1> + <title>Examples</title> + + <example> + <title>Logging environment variables provided by systemd to services</title> + + <programlisting># systemd-run env +Running as unit: run-19945.service +# journalctl -u run-19945.service +Sep 08 07:37:21 bupkis systemd[1]: Starting /usr/bin/env... +Sep 08 07:37:21 bupkis systemd[1]: Started /usr/bin/env. +Sep 08 07:37:21 bupkis env[19948]: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin +Sep 08 07:37:21 bupkis env[19948]: LANG=en_US.UTF-8 +Sep 08 07:37:21 bupkis env[19948]: BOOT_IMAGE=/vmlinuz-3.11.0-0.rc5.git6.2.fc20.x86_64</programlisting> + </example> + + <example> + <title>Limiting resources available to a command</title> + + <programlisting># systemd-run -p IOWeight=10 updatedb</programlisting> + + <para>This command invokes the <citerefentry + project='man-pages'><refentrytitle>updatedb</refentrytitle><manvolnum>8</manvolnum></citerefentry> + tool, but lowers the block I/O weight for it to 10. See + <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for more information on the <varname>IOWeight=</varname> property.</para> + </example> + + <example> + <title>Running commands at a specified time</title> + + <para>The following command will touch a file after 30 seconds.</para> + + <programlisting># date; systemd-run --on-active=30 --timer-property=AccuracySec=100ms /bin/touch /tmp/foo +Mon Dec 8 20:44:24 KST 2014 +Running as unit: run-71.timer +Will run service as unit: run-71.service +# journalctl -b -u run-71.timer +-- Journal begins at Fri 2014-12-05 19:09:21 KST, ends at Mon 2014-12-08 20:44:54 KST. -- +Dec 08 20:44:38 container systemd[1]: Starting /bin/touch /tmp/foo. +Dec 08 20:44:38 container systemd[1]: Started /bin/touch /tmp/foo. +# journalctl -b -u run-71.service +-- Journal begins at Fri 2014-12-05 19:09:21 KST, ends at Mon 2014-12-08 20:44:54 KST. -- +Dec 08 20:44:48 container systemd[1]: Starting /bin/touch /tmp/foo... +Dec 08 20:44:48 container systemd[1]: Started /bin/touch /tmp/foo.</programlisting> + </example> + + <example> + <title>Allowing access to the tty</title> + + <para>The following command invokes + <citerefentry project='man-pages'><refentrytitle>bash</refentrytitle><manvolnum>1</manvolnum></citerefentry> + as a service passing its standard input, output and error to the calling TTY.</para> + + <programlisting># systemd-run -t --send-sighup bash</programlisting> + </example> + + <example> + <title>Start <command>screen</command> as a user service</title> + + <programlisting>$ systemd-run --scope --user screen +Running scope as unit run-r14b0047ab6df45bfb45e7786cc839e76.scope. + +$ screen -ls +There is a screen on: + 492..laptop (Detached) +1 Socket in /var/run/screen/S-fatima. +</programlisting> + + <para>This starts the <command>screen</command> process as a child of the + <command>systemd --user</command> process that was started by + <filename>user@.service</filename>, in a scope unit. A + <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry> + unit is used instead of a + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + unit, because <command>screen</command> will exit when detaching from the terminal, + and a service unit would be terminated. Running <command>screen</command> + as a user unit has the advantage that it is not part of the session scope. + If <varname>KillUserProcesses=yes</varname> is configured in + <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + the default, the session scope will be terminated when the user logs + out of that session.</para> + + <para>The <filename>user@.service</filename> is started automatically + when the user first logs in, and stays around as long as at least one + login session is open. After the user logs out of the last session, + <filename>user@.service</filename> and all services underneath it + are terminated. This behavior is the default, when "lingering" is + not enabled for that user. Enabling lingering means that + <filename>user@.service</filename> is started automatically during + boot, even if the user is not logged in, and that the service is + not terminated when the user logs out.</para> + + <para>Enabling lingering allows the user to run processes without being logged in, + for example to allow <command>screen</command> to persist after the user logs out, + even if the session scope is terminated. In the default configuration, users can + enable lingering for themselves:</para> + + <programlisting>$ loginctl enable-linger</programlisting> + </example> + + <example> + <title>Variable expansion by the manager</title> + + <programlisting>$ systemd-run -t echo "<${INVOCATION_ID}>" '<${INVOCATION_ID}>' + <> <5d0149bfa2c34b79bccb13074001eb20> + </programlisting> + + <para>The first argument is expanded by the shell (double quotes), but the second one is not expanded + by the shell (single quotes). + <citerefentry project='man-pages'><refentrytitle>echo</refentrytitle><manvolnum>1</manvolnum></citerefentry> + is called with [<literal>/usr/bin/echo</literal>, + <literal><></literal>, <literal><${INVOCATION_ID}></literal>] as the argument array, and then + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> + generates <varname>${INVOCATION_ID}</varname> and substitutes it in the command-line. This substitution + could not be done on the client side, because the target ID that will be set for the service isn't + known before the call is made.</para> + </example> + + <example> + <title>Variable expansion and output redirection using a shell</title> + + <para>Variable expansion by + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> + can be disabled with <varname>--expand-environment=no</varname>.</para> + + <para>Disabling variable expansion can be useful if the command to execute contains dollar characters + and escaping them would be inconvenient. For example, when a shell is used:</para> + + <programlisting>$ systemd-run --expand-environment=no -t bash \ + -c 'echo $SHELL $$ >/dev/stdout' +/bin/bash 12345 + </programlisting> + + <para>The last argument is passed verbatim to the + <citerefentry project='man-pages'><refentrytitle>bash</refentrytitle><manvolnum>1</manvolnum></citerefentry> + shell which is started by the service unit. The shell expands <literal>$SHELL</literal> to the path of + the shell, and <literal>$$</literal> to its process number, and then those strings are passed to the + <command>echo</command> built-in and printed to standard output (which in this case is connected to the + calling terminal).</para> + </example> + + <example> + <title>Return value</title> + + <programlisting>$ systemd-run --user --wait true +$ systemd-run --user --wait -p SuccessExitStatus=11 bash -c 'exit 11' +$ systemd-run --user --wait -p SuccessExitStatus=SIGUSR1 --expand-environment=no \ + bash -c 'kill -SIGUSR1 $$'</programlisting> + + <para>Those three invocations will succeed, i.e. terminate with an exit code of 0.</para> + </example> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-mount</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |